1. Field of the Invention
The present invention relates to the field of image processing, and particularly relates to an image feature extraction method and an image extraction system.
2. Description of the Related Art
A panoramic image captured by a panoramic camera, for example, an equirectangular image is usually distorted, especially at the positions near two poles, as shown in FIG. 1 which illustrates an example of the panoramic image captured by the panoramic camera. It can be seen from FIG. 1 that the objects in the panoramic image are distorted, especially the objects at the top and bottom portions; for example, the human face at the bottom portion is distorted. As a result, in this kind of distorted panoramic image, it is difficult to carry out image feature extraction and object detection, especially with respect to the distorted objects at the positions near two poles.
Generally, in the conventional techniques, there are two types of methods for carrying out object detection in the panoramic image. The first type of method is conducting projection transformation to correct the panoramic image so as to remove distortions thereof, and then conducting image feature extraction and object detection with respect to the corrected panoramic image. However, the problem of this type of method is that there doesn't exist a perfect projection transformation approach by which not only shapes but also straight lines may be kept. Of course, it is also possible to correct the panoramic image by respectively conducting projection transformation at different positions thereof, but this kind of approach is inefficient. The second type of method is collecting samples at different positions so as to carry out training. For example, it is possible to collect samples at the positions near two poles of the panoramic image so as to carry out the training of image feature extraction, so that it is possible to conduct object detection on the basis of this kind of training. However, the problem of this type of method is that the process of collecting samples is too complicated and very difficult, especially with respect to the objects having various shapes.
Therefore, in order to be able to directly and efficiently conduct image feature extraction and object detection with respect to the panoramic image, it is desirable to propose a new method in which it is not necessary to conduct projection transformation or collect samples at different positions thereof.